An electronic device (semiconductor device) has been widely used in various electronic equipments. The electronic device is sometimes charged with static electricity, while it is in a process of production or while it is mounted on an electric equipment. Discharge of the static electricity can cause a breakdown of the electronic device. In view of the circumstances, when designing the electronic device, it is necessary to secure sufficient withstand static electricity.
In recent years, an electronic device such as a source driver LSI or a gate driver LSI has been used in a large liquid crystal panel. This causes the electronic device to have been developed so as to have multiple output terminals. At the same time, for the purpose of cost reduction, the electronic device has been miniaturized so that a chip of the electronic device can be reduced in size. This causes a protection element, a power supply line, and a GND line to be reduced in size, width, and thickness. As a result, an electrostatic discharge breakdown of the electronic device becomes easy to occur.
In regard to a car-mounted display device and the like, a semiconductor element is required to have a much more strict standard. In view of this, an electrostatic discharge withstand voltage evaluating device and an electrostatic discharge withstand voltage evaluating method have grown in importance in an electrostatic discharge breakdown test.
In the electrostatic discharge breakdown test, an electrostatic discharge of the electronic device is simulated for the purpose of measuring electrostatic discharge breakdown withstand of the electronic device. The electrostatic discharge breakdown test measures the electrostatic discharge breakdown withstand of the electronic device by preparing a model for recreating how the electrostatic discharge breakdown occurs.
Source models of the electrostatic discharge breakdown are roughly classified in accordance with a contributing factor causing the electrostatic discharge breakdown, into HBM (human-body model), CDM (charged-device model), and MM (machine model).
In the HBM and MM, the electronic device is not electrically charged itself. In the HBM and MM, an electrostatic discharge breakdown occurs in the electronic device in response to an occurrence of electric discharge caused by direct contact of other object (such as human or machine) with a terminal of the electronic device.
In the CDM, an electrostatic discharge breakdown occurs in the electronic device in response to an occurrence of electric discharge caused by direct contact of an external conductor with a terminal of the electronic device, while the electronic device itself is electrically charged by a friction, a dielectric charging, or direct contact with an electrically-charged body.
As described above, at the time of designing, an electronic device is subjected to a measurement of electrostatic discharge breakdown withstand with the use of an evaluating device that recreates any one of the above-mentioned breakdown models. By this measurement, it is confirmed that no electrostatic discharge breakdown has occurred in the electronic device in a process of production of the electronic device or while the electronic device is mounted on an electronic equipment.
Such a method for evaluating an electrostatic discharge breakdown withstand of a semiconductor device by recreating any one of the breakdown models is disclosed in Patent Literature 1, for example. A conventional method for evaluating a semiconductor device and the conventional method of Patent Literature 1 are described below with reference to FIGS. 11 and 12.
FIG. 11 is a view illustrating a conventional arrangement for evaluation of the HBM and MM.
In a semiconductor device 201, a reference terminal (external electrode 202a) and a measuring terminal (external electrode 202d) are selected from external electrodes 202a through 202d. A switch 203 is switched to a power supply 205 so that a capacitor 204 is charged by a high voltage supplied from the power supply 205. Then, the switch 203 is switched to the semiconductor device 201 from the power supply 205 so that the capacitor 204 causes electric discharge between the reference terminal and the measuring terminal of the semiconductor device 201. This causes recreation of a breakdown of the semiconductor device 201, thereby evaluating an electrostatic discharge breakdown withstand.
FIG. 12 is a view illustrating an arrangement for evaluation of the CDM suggested in Patent Literature 1.
A semiconductor device 301 includes an external electrode 302 and a contact electrode 304 that is electrically isolated from the external electrode 302 by an insulative surrounding section 303. A switch 305 is turned on so that the contact electrode 304, which is part of the semiconductor device 301, is electrically charged by a power supply 306. Then, an electric discharge occurs between the contact electrode 304 and the external electrode 302. This causes recreation of a breakdown of the semiconductor device 301, thereby evaluating an electrostatic discharge breakdown withstand.
The electrostatic discharge breakdown of an electronic device has been conventionally prevented, by carrying out the electrostatic discharge breakdown test as described above or by taking measures such as provision of a protection circuit in the electronic device.
Citation List
Patent Literature 1
Japanese Unexamined Patent Publication, Tokukaisho, No. 57-80577 (Publication Date: May 20, 1982)